Belair is the only place I'm aware of that assigns you chairs upon check-in. I think, when walking from Divi to Belair's beach restaurant, I also saw a sign stating chairs were for guests only.

We've given up at getting a chair at one of the pools, when staying at Divi. During a 2 week stay couldn't get any. I even went out at 4;30 am to the pool behind the unit we were in and found all covered with towels. When we went by again I saw a woman come to the pool pick up 3 towels and replace them with new towels. I guess Divi has no rules.